Prevent trace mutation during critical path computation

[Copilot]

The critical path algorithm was mutating the original trace's spans by modifying childSpanIds arrays and references during computation, breaking immutability guarantees.

Changes

New types for isolated computation:

• Added CPSpan type containing only fields needed for critical path computation (spanID, startTime, duration, references, childSpanIds)
• Added CPSpanReference type for span references within CPSpan objects

Utility functions for CPSpan creation:

• Created utils/cpspan.tsx module with createCPSpan() and createCPSpanMap() helper functions
• Centralized CPSpan object creation to ensure consistent defensive copying across the codebase

Updated critical path functions:

• criticalPathForTrace() now uses createCPSpanMap() to create defensive copies before processing
• Updated utility functions (getChildOfSpans, sanitizeOverFlowingChildren, findLastFinishingChildSpan, computeCriticalPath) to operate on CPSpan instead of Span
• getChildOfSpans now checks childSpanIds.length > 0 instead of using a separate hasChildren field

Example of the fix:

// Before: Modified original trace spans
const spanMap = trace.spans.reduce((map, span) => {
  map.set(span.spanID, span);  // Direct reference
  return map;
}, new Map<string, Span>());

// After: Creates isolated copies using utility function
const spanMap = createCPSpanMap(trace.spans);

Test coverage:

• Added unit tests verifying original trace remains unmodified after critical path computation
• Updated existing tests to use centralized createCPSpan() utility
• Enhanced test descriptions to clearly indicate what each test case validates (e.g., "child starts after parent ends - child dropped")

Original prompt

The funciton criticalPathForTrace() in packages/jaeger-ui/src/components/TracePage/CriticalPath/index.tsx, and specifically the util functions it calls, is modifying the underlying trace structure. Even though it creates a new spanMap, the util functions are manipulating the inside parts of the spans, like references[]

1. I want to add unit tests to ensure that criticalPathForTrace() does not modify the trace passed to it.
2. I want to create a helper type CPSpan (for "critical path span") which has childSpanIds array and remove that array from SpanData in packages/jaeger-ui/src/types/trace.tsx
3. Let criticalPathForTrace() create Map<string, CPSpan> and pass it to util functions, such that the original trace.spans are not modified

Before submitting PR:

• Run npm run prettier to format the changed code.
• Make sure npm test and npm run lint are successful

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[yurishkuro]

I think hasChildren can be dropped, code can check if(span.childSpanIds) for the same outcome, less data to maintain

[Copilot]

Done in commit 1d5832f. Removed hasChildren from CPSpan type and updated code to check childSpanIds.length > 0 instead.

[yurishkuro]

this function seems to be needed in many places, extract it into utility module and use every time we're creating CPSpan

[Copilot]

Done in commit 1d5832f. Extracted createCPSpan() and createCPSpanMap() functions into a new utility module at utils/cpspan.tsx and updated all test files to use it.

[yurishkuro]

add a description string to each test case (illustrating what is specific about it compared to other tests) and include that description in the test name in it()

[Copilot]

Done in commit 1d5832f. Added descriptive strings to each test case (e.g., "child starts after parent ends - child dropped") that appear in both the test suite name and individual test names.

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• iojs.org
  • Triggering command: /usr/bin/curl curl -q --fail --compressed -L -s REDACTED -o - (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.45%. Comparing base (1634eef) to head (1d5832f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3271   +/-   ##
=======================================
  Coverage   97.45%   97.45%           
=======================================
  Files         268      269    +1     
  Lines        8364     8369    +5     
  Branches     2211     2212    +1     
=======================================
+ Hits         8151     8156    +5     
  Misses        210      210           
  Partials        3        3           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.